The beginning and ending dates as well as the number of days of vegetation period were determined. Average monthly air temperature values of particular months during the vegetation period were analysed. The direction and significance of tendency of changes were determined on the basis of linear trend equations. Thermal vegetation period in central-eastern Poland began around March 28^th and lasted till October 30^th. South-western part of the area examined was characterised by the highest average air temperature of the vegetation period (IV-X), while north-eastern part – by the lowest. In most of the stations analysed, statistically significant changes of air temperature were noted in April, July and August. The highest increase of this parameter (on average of 0.7^oC for 10 years) was noted in April. In stations located in the eastern part of the region examined a significant increase of temperature (on average of 0.4^oC for 10 years) occurred also in October.